Fuel compounds, inhibiting effects

The catalytic reduction of the radicals, particularly the O atom, by sulfur compounds will generally reduce the rates of reactions converting atmospheric nitrogen to NO by the thermal mechanism. However, experiments do not permit explicit conclusions [21], For example, Wendt and Ekmann [46] showed that high concentrations of S02 and H2S have an inhibiting effect on thermal NO in premixed methene-air flames, while deSoete [47] showed the opposite effect. To resolve this conflict, Wendt el al. [48] studied the influence of fuel-sulfur on fuel-NO in rich flames, whereupon they found both enhancement and inhibition. 

Effect of Additives. One of the first attempts to solve the preignition problem by additives was the use of tributyl phosphite, claimed in a patent by Campbell (14) This compound inhibited the catalytic activity of lead compounds in promoting the glowing of carbon. A later patent issued to Withrow claimed that trimethyl phosphate and trimethyl phosphite also are effective as fuel additives in inhibiting surface ignition due to leaded deposits (94). Street, in 1952, ran tests with tricresyl phosphate as an additive in leaded fuel and reported that the phosphorus compound affected the occurrence of lead compounds in the end-gas region of the combustion chamber (80). 

A major challenge in the ultradeep desulfurization of hydrocarbon fuels is the inhibiting effects of fuel components (e.g., nitrogen compounds) and reaction products (e.g., hydrogen sulfide). While this area has been studied in catalysis literature, it is expected to gain increased attention because of the severity of the new sulfur specifications. ... 

The results are shown in Figure 6. It can clearly be seen that 3-methylindole and 1,4-dimethylcarbazole are not major inhibitors, whereas acridine is. The three component blend behaves essentially as an additive combination of the three different N-compounds. There are also indications to the effect that acridine strongly inhibits the conversion of 1,4-dimethylcarbazole. In the absence of acridine, a high degree of conversion was obtained even for this low reactivity alkylcarbazole. The results indicate that alkylcarbazoles are not the major species of concern in HDS inhibition, even though they are the major species detected in hydrotreated diesel fuels. This suggests that there may be some components of diesel fuels that inhibit both HDN of alkylcarbazoles and HDS of alkyldibenzothiophenes. To see whether or not this is the case, additional studies were conducted on the N-free diesel fuel. 

Ethers, esters, amides and imidazolidines containing an epithio group are said to be effective in enhancing the antiwear and extreme pressure peiformance of lubricants. Other uses of thiiranes are as follows fuel gas odorant (2-methylthiirane), improvement of antistatic and wetting properties of fibers and films [poly(ethyleneglycol) ethers of 2-hydroxymethyl thiirane], inhibition of alkene metathesis (2-methylthiirane), stabilizers for poly(thiirane) (halogen adducts of thiiranes), enhancement of respiration of tobacco leaves (thiirane), tobacco additives to reduce nicotine and to reduce phenol levels in smoke [2-(methoxymethyl)thiirane], stabilizers for trichloroethylene and 1,1,1-trichloroethane (2-methylthiirane, 2-hydroxymethylthiirane) and stabilizers for organic compounds (0,0-dialkyldithiophosphate esters of 2-mercaptomethylthiirane). The product of the reaction of aniline with thiirane is reported to be useful in the flotation of zinc sulfide. 

Poisoning of deNOx catalysts by SO2 could also be a problem since diesel fuels contain small amounts of sulfur compounds. Only a few studies deal with this subject [11-13]. It appears from the literature that for Cu catalysts the use of MFI as a support reduces the inhibition by SO2. Support effects also appear in the case of Co since Co/MFI is much less sensitive to SO2 than Co/ferrierite [13]. Since this support effect may be related to acidity, it becomes important, to investigate the influence of SO2 on the properties of Cu catalysts supported on Si02, AI2O3, MFI, BEA and unpromoted or sulfate promot Ti02 and Zr02- These latter have been reported active for deNOx [14]. 

Inhibition technology also has been used recently by two other groups. Urea as an aqueous solution added to the fuel has been found to be very effective as an inhibitor of PCDD/F in a pilot and technical plant. Furthermore, other A -compounds and A-compounds, such as sulfur dioxide, ammonia, dimethyla-mine, and methyl mercaptan sprayed as gaseous inhibitors in the flue gas, seem to be a promising technique for preventing the formation of PCDD/F in waste incineration. 

Fuel sulfur can decompose alkyl lead compounds and can diminish the effectiveness of lead compounds at inhibiting combustion knock. The effect of fuel sulfur at degrading alkyl lead compounds can be rated as follows ... 

Corrosion-inhibiting properties of fuel stabilizers can be a secondary effect of the dispersing action of a fuel stabilizer. By functioning as a dispersant, sludge and water are held in suspension and prevented from initiating metal surface corrosion. Also, some stabilizer dispersants can form a thin film on the metal surfaces of fuel system components. This film-forming property enables the stabilizer-dispersant to function in corrosion control. A typical oil-soluble dispersant compound is shown in FIGURE 6-3. 

In addition to refining techniques, compounds identified as wax crystal modifiers are available for use in contending with the effects of wax in fuels. Wax crystal modifiers, also called pour point depressants or cold flow improvers, are typically polymeric compounds which have the ability to crystallize with fuel wax as it forms. By co-crystallizing with wax, the modifiers typically effect a change in the size, shape, and conformation of wax crystals. Other wax crystal modifiers function by dispersing or inhibiting the nucleation or growth of wax crystals within a fuel or oil. 

Use of fuel containing effective oxidation inhibiting and metal deactivating compounds can minimize gums and sludge... 

Additives have been shown to effect decreases in coke deposits. Small amounts of organometallic compounds and commercial fuel-oil additives have been shown to decrease coke weight. Metallic compounds in excess can result in increased deposition because of the metal oxide, and some of these compounds have also been reported to cause metal corrosion, as have sulfur compounds. Results of investigations with additives to inhibit coke formation are not conclusive enough at present to justify their acceptance. 

Radical formation is frequently an occurrence that modifies the chemical stmeture of many substances with negative effects on their overall performance. Thus, for example, polymeric materials may reduce or lose their mechanical properties, turn yellow, etc. hydrocarbon fluids (lubricants, fuels) may give rise to precipitation of solids unsaturated compounds (monomers, etc.) may produce undcsired reactions during storage. As a consequence, the need to inhibit radical generation is in many ca.scs of vital importance. 

Mechanism. No single mechanism explains the action of all fire retardants, so they probably work through a combination of several mechanisms. The mechanisms of fire retardants in wood involve a complex series of simultaneous reactions whose products may affect subsequent reactions. Pyrolysis of cellulose involves dehydration, depolymerization, decarbonylation, decomposition of smaller compounds, condensation, and other reactions. These pyrolysis reactions occur both in the solid phase and vapor phase. Addition of fire retardants will alter the reactions however, this alteration will depend on the additives, the material, and the thermal-physical environment. The presence of oxygen adds subsequent and competitive oxidation reactions to the above series. These oxidative reactions can take place in both the solid and vapor phases. Evidence indicates that most fire retardants reduce combustible volatiles production and limit combustion to the solid phase. The best retardants also inhibit solid-phase oxidation to effectively remove the fuel from the fire. 

Naphthalene and its derivatives are one of the more dominant aromatics present in various diesel and jet fuel feedstocks. Therefore, several investigators have reported the influence of naphthalene on HDS of model compounds. One of the first reports was by Lo who found naphthalene to weakly inhibit the conversion and selectivity of the HDS of DBT. Similarly, LaVopa and Satterfield found little effect of naphthalene and phenanthrene on the HDS of thiophene. Other researchers have, however, found naphthalene to be a stronger inhibitor of HDS activ-ity. Nagai and Kabe, in fact, found naphthalene to significantly reduce catalyst selectivity for the hydrogenation pathway.Isoda et al., on the basis of similar selectivity inhibition, concluded that naphthalene severely inhibits the hydrogenation active sites in a... 

Phosphodiesterase is inhibited by methyixanthines, a class of compounds that includes caffeine. Would the effect of a methyixanthine on fuel metabolism be similarto fasting orto a high-carbohydrate meal ... 

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